May 17th 2017 by Alex Zhou

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6.1.1:
resources that need to be managed within a computer system
RAM
Secondary storage(HDD/SSD/optical drives)
CPU
Network
Screen resolution
Sound/Graphics
Bandwidth


In the processor: cores
Each processor has at least 1 ALU or core. If you have 2 ALUs you can do two operations at once.

Sound processor:
  • Sound reproduction is done by a separate processor,freeing up the CPU to do other calculations.
  • Can also contain a bank of ‘sampled’ sounds to reproduce better quality music/audio
Effects on system if limited:
  • CPU is taxed with having to processes sounds, slowsdown system overall.
  • Overall quality is not as high as in a system with adedicated sound processor.

Graphics processor (GPU)
Does complex graphicprocessing (like 3D rendering)
Effect on system if too limited:
  • If CPU has to do graphicsprocessing, it will take longeror be limited.

6.1.2
Types of Computers

Mainframes:
Processor: Thousands of cores
Primary memory: Vast amounts
Secondary memory: Vast amounts
Common use:
  • Used in large companies
  • Used in banks, corporations
  • Used to ‘virtualize’ smallercomputers
  • Main players: CRAY/IBM
Servers
Processor: Many high spec PCsrunning in parallel (3-4GHz)
Primary memory: Big capacity(32GB+ per machine)
Secondary memory: Terabyte permachine
Common use:
  • Used to ‘serve’ networks
  • Used as data centers for ‘cloudstorage’
  • Size varies according to use

PCs
Processor: Single processor(multiple cores) 1-4 GHz
Primary memory: 2-16 GB
Secondary memory: 256 GB to 2 TB
Common use:
  • Used in companies/schools(where portablility is not needed)
  • Can be expanded by addingexpansion cards (graphics cards)
  • Used to be the most commontype of personal computer

Sub-laptops (netbooks)
Processor: Single/multiple core (1-2 GHz)
Primary memory: 1-2 GB
Secondary memory: Normally SSD – 16-128 GB
Common use:
  • Fueled by ‘netbook boom’ of early2000s (before tablets)
  • Runs stripped down OS (Linux,Chrome OS)
  • Portablity and battery life are key features
Cell phones/mobiles
Processor: Single/MulticorePrimary memory: 1-3 GB
Secondary memory: Usually limited, but can be upgraded (MicroSD card)

Common use:
  • Most common personal computingdevice in the world
  • Getting more capable, rivaling PCs/laptops
  • Biggest constraint is screen size andinput options (lack of physical keyboard)
Personal digital devices
Who uses this anyway?

6.1.3
Hardware limitations:
CPU
GPU
Memory
Storage
Camera
Screen

6.1.4
e.g.
  • User time wasted if the primary memory is too small or processor speed inadequate.
  • Multi-access and multi-programming environments should be considered as well as single-user systems.

  • Multi-programming system = system that can have differentprograms (apps) installed
  • Single programming system = can only run one program/setof programs

  • Either many users on the same machine
  • Or many users connected to the same network


6.1.5
  • Hardware management
    • Communicating with all hardware
    • Through the use of drivers (specially written, individualized) ‘translation’ programs, the other programs (and ultimatelythe user) can use and control peripheral devices (like akeyboard, mouse, printer, etc.)
  • Resource monitoring
    • processor time, memory usage, etc.
  • Coordinating concurrent processing•
    • multiple programs (processes) running at the same time
  • Memory management
    • each program has their own space in memory
    • The OS has to ensure thateach process (program)runs in its own allocatedmemory space.
    • If programs interfere witheach other’s memory space it could cause many problems including corruption and security issues.
  • Virtual Memory:
    • Paging / Swapping•
      • Moving program data between memory and disk•
    • Optimizations•
      • Whole programs do not have to fit in memory contiguously (all in one section)
      • Prevents memory segmentation
      • Pre-emptive paging
  • Managing (secondary) storage
    • The OS manages the secondary storage by providing structure and access methods to these structures
    • We often refer to this as the folder-structure but in some OS it is referred to as the directory structure.
    • The OS also manages the security access of these folders
  • Interface:
    • Graphical User Interface Operating System
    • Command Line Operating System
Mechanism:
Time-slicing
  • With a multi-user system, a time-slice is the set amount of processing time each user gets.
  • With a single-user system, a time-slice is the set amount of processing time each program gets.
  • Slices (also called threads) are alternately processed to givethe illusion of many tasks happening at once.

Interrupt handling
  • An interrupt handler is a function in of the OS or a device drive
  • In general, interrupts are used to handle high-priority conditions that require the interruption of the current code the processor is executing.
  • For example, pressing a key on a keyboard, or moving themouse, triggers interrupts that call interrupt handlers whichread the key, or the mouse's position, and copy the

6.1.7
Resource management techniques:
Scheduling:
  • The work could be processes which are in turn scheduled onto hardware resources such as processors, network linksor expansion cards.
  • The algorithm used may be as simple as round-robin in whicheach process is given equal time (for instance 1 ms, usuallybetween 1 ms and 100 ms) in a cycling list. So, process Aexecutes for 1 ms, then process B, then process C, then backto process A.
Policies
  • The policies what is to be done while the mechanismspecifies how it is to be done.
  • For instance, the timer construct (limiting the time a processcan use the CPU for) thereby ensuring CPU protection is mechanism.
  • On the other hand, the decision of how long the timer is setfor a particular user is a policy decision.
  • The separation of mechanism and policy is important toprovide flexibility to a system.
Polling
  • Polling is the process where the computer or controllingdevice waits for an external device to check for its readinessor state, often with low-level hardware.
  • For example, when a printer is connected via a parallel port,the computer waits until the printer has received the nextcharacter.

6.1.8
Discuss the advantages of producing a dedicated operating system for a device

Size:
  • To make devices easier to use to their audience, more tailored to their needs.Eliminating certain aspects of OS, which are not needed, can reduce the size of OS, and thus reduce amount of secondary memory and RAM.
  • For example, Apple’s iPod, iPhone and iPad all run the iOS mobile operating system while the desktop or laptop computer uses Mac OS.
Speed:
  • Efficiency is maximized when a dedicated OS is used, since it focuses on a specific function.
Customization:
  • A dedicated system has a higher level of security.
  • For example, banks or national institutions can use a dedicated OS to prevent cyber attacks.